1. Field of the Invention
The present invention relates to a slat angle adjusting device, and more particularly to a slat angle adjusting device for a venetian blind and one that is smooth in operation.
2. Description of Related Art
With reference to FIGS. 5 and 6, a conventional slat angle adjusting device for a Venetian blind in accordance with the prior art comprises a body, a pinion (33), a drive axle (34), a rotating rod (36) and a roller (38). The body is composed of a base (30) and a cover (32). A positioning base (302) is formed on the top of the base (30) to engage with a headrail of the venetian blind to mount the adjusting device to the headrail. The pinion (33) is rotatably mounted inside the body and has a non-circular through hole defined through the pinion (33). With the through hole, the pinion (33) engages with a tilt rod with a non-circular cross section to drive the tilt rod to rotate with the pinion (33). The drive axle (34) is rotatably mounted inside the body and has at least one helical tooth (342) to engage with the pinion (33). The drive axle (34) further has an engaging end provided with multiple teeth (344). The rotating rod (36) is rotatably attached to the body and has an inner end extending into the body. The inner end of the rotating rod has multiple teeth (362) engaging with the teeth (344) on the drive axle (34). The roller (38) is attached to the rotating rod (36), and a tilt cord is mounted around the roller (38) to rotate the roller (38) when the cord is pulled.
Accordingly, when the tilt cord is pulled, the tilt rod is rotated with the transmission of the roller (38), the rotating rod (36), the drive axle (34) and the pinion (33). With the rotation of the tilt rod, the angle of slats of a Venetian blind is adjusted.
Each helical tooth (342) on the drive rod (34) of the conventional adjusting device is a continuous structure, and the drive axle (34) is formed in a die-casing process by a mold combined with two mold elements. However, burs are easily formed on the helical teeth (342) at a location corresponding to the conjunction of the mold elements, and the transmission between the drive axle (34) and the pinion (33) is not smooth due to those burs.
In addition, with reference further to FIG. 7, the teeth (344,362) on the drive axle (34) and the rotating rod (36) of the conventional device have a substantially triangular cross section. With the triangular teeth (344,362), the clearances between the teeth (344,362) on the drive axle (34) and the rotating rod (36) are reduced, such that the transmission between the drive axle (34) and the rotating rod (36) is not smooth when tiny inaccuracies in sizes or shapes occur in the teeth (344,362).
Furthermore, the base (30) and the cover (32) of the conventional body do not have any positioning device, such that to precisely combine the base (30) with the cover (32) is troublesome and time-consuming. Moreover, the engaging relationships between the pinion (33), the drive axle (34) and the rotating rod (36) will fail if the base (30) is not precisely combined with the cover (32).
To overcome the shortcomings, the present invention tends to provide a slat angle adjusting device to mitigate or obviate the aforementioned problems.